In the metric system, series of standard paper sizes based on portions of a square meter. (A square meter is the area used to determine paper grammage, the metric equivalent of basis weight. Grammage is expressed as grams per square meter [g/m2].) In the A series, the length-to-width ratio is maintained from size to size, and the area varies from size to successive size by a factor of 2 or H. The standard size that corresponds most closely to the United States standard letter size of 8H x 11 is A4-size paper. There is also a B series of paper sizes that are intermediate A series sizes. The sizes and area of A series paper (from sizes A0 to A8) are as follows:
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See also Grammage, B Series and ISO Paper Sizes.